How consistent are adaptation strategies with ongoing climatic and environmental changes in the Vietnamese Mekong Delta: A systematic review

The densely populated Vietnamese Mekong Delta (VMD), the third-largest delta globally, plays a vital role in regional and global food security. However, it has undergone significant climatic and environmental changes over recent decades, driven by intricate interactions between global climate change and human activities within the VMD and its upstream river basin. The rapid evolution and quantification of these changes, as evidenced by recent scientific studies, suggest continued and substantial alterations in the near future, posing a serious threat to the delta's sustainability. Given the urgency of these environmental transformations, it is imperative to evaluate the extent to which current climate adaptation policies and delta development plans integrate state-of-the-science knowledge on environmental changes and future trajectories. To assess the coherence between scientific knowledge and prevailing policy directives shaping delta development, we conducted a systematic review of 27 existing adaptation plans and/or strategies for the VMD. This review, supplemented by an examination of projects in five provinces identified as hotspots for relative sea-level rise and saltwater intrusion, is enriched by an analysis of evolutionary trajectories of various key policies and adaptation plans over time, offering valuable insights into their historical influence on the delta. We found that while most documents acknowledge the reality of climate change, they often lack clarity regarding which dimensions of its environmental effects are addressed. The predominant focus tends to be on issues related to saltwater intrusion, floods, and seasonal inundation, whereas the existential threat posed by accelerating land subsidence and consequent relative sea-level rise receives comparatively less attention. Moreover, the significant role of sediment starvation, particularly due to sand mining, in exacerbating saltwater intrusions in the VMD’s estuary system is largely overlooked. Our results show that the climatic and environmental pressures garnering the most attention are typically those resulting in obvious, direct, and event-based impacts on the delta's population and livelihoods. However, these pressures often serve as symptoms of underlying, steadily escalating, longer-scale processes, such as land subsidence or sediment starvation, which are inadequately addressed in current policy steering documents and adaptation plans. Neglecting these potentially existential environmental pressures not only leads to missed opportunities for adaptation and mitigation in current delta development but also jeopardizes the delta's long-term sustainability.